Water tube steam generator



Aug. 23, 1938. M. SCHMIDT WATER TUBE STEAM GENERA'TOR Filed July 1'7. 1935 5 Sheets-Sheet 1 NVEN nw' MAPTN SCHMDT ORNEYS Aug. 23, 1938.

M. SCHMIDT WATER TUBE STEAM GENEHATOR 5 Sheets-Sheet 2 .Se/miat ATT NEYS 1 5 mi a Filed July 17, 1955 1938- M. SCHMIDT 2,127,787

WATER TUBE STEAM GENERATOR Filed July 17, 1955 5 Sheets$heet 4- Fig. 10. I

IvvEvToR MARTN ScHMDT A T TORNEYS G a-% a Aug.23, 1938. M. SCHMIDT WATER TUBE STEAM GENERATOR 5 Sheets-Sheet 5 Filed July 17. 1935 fig. 17.

NVENTOR Mm'Scmor A an EY5- G M then force its way through the snperincomh drums, but on the central-y, 'flows continuously and automatically either in each :individual circulation unit or in indlviclual groups of such units, or again, through the entire tube system.

The water must therefore always take a, definite path predetermlned by the constmctlcn so that a uniform cooling of all the tube& is assurecl.

Since in the new boller, even under different conditions of load and operation, for example, even with varyng quantities oi' water in the ch'- culation units, the riser parts of the circulatlcn units are well cooled, the heating surfaces can he worked at a high rating.

The new holer comblnes the essential advantages of known flash hollers and water-tulle boilers witl'out the dlsadvantages mentloned above cu'rlng in bollers of these types.

ed with'the flash boller, the new Agnlshed particularly by its lower ul lncreaseol safety ln operation. 3, lt is especially suitable even for '3 virtue of its small weight, a&

hre, and can in acloiton he aallnllecl in 'power lnstallatlons aa nn per-zl; leads.

.Also Wl clly varv'ng leads, ene.: in rail motor cars, a Safer operation without application of compllcate. regulatins anna is ensu'ecl and; a further latitncle in the rt" content is lcled so to prevent tl. hand uncle le loco of Water on the c hand an m nisslhle eva-;meeting 'the in the circu. n unlts.

On account. of the lower degree of sensitiv of the new hcller, the feed, as above rn n can he to certain extent acceleratcc or t' layed; in "ich, if the feed 'evrop steam-geneatng tuhes are not lmmeclate dangered.

It will he seen that in a water tn according to the present inventon, it ic to provide eil'cient appan 'for sem steam anti erancl efu iG' 'cart of inventlon denis with apparatus which, :a able for the specific use referred to, la a ceble generally ?for separa'ting gas &nel/or va from a mlxtnre of gas and or vapor and llom flowing through a tube, but for con part of the invention will he descrlheo! helcw trucks an vantageonu auxliary i" cent where otherwise indicatecl.

Hitherto the separation of steam from mi r ture of steam and water produced in ever-lo tubes, has been commcnly eflected in. a stcarnand-water drum into which the open encls of evaporating tubes deliver.

If the dlscharge of these tulles lies below the surface of the water, the steam generate&

layer and in consequence must entraln a wmtoy of water, but even if the evapomtlng 'cases chargeinto the steam space of the (ir-nm, the steam must stlll contain a large pronart-lon of water because, in the mixture ejected, the stearc and water are in a state of relative turhule-nce and so prevent the desh-ed sudden separation ci the steam and water particles.

For such reasons, in order to obtan dry steam, steam separators or driers have been constructecl which for the separation of the steam and water rely either on the impact prlnciple, or on the action of centriugal force, or on sudden changes o! direction.

In all these cases, however, the disadvantage is present that the kinetic energy in the steam-water mixture at the upper end of the evaporatlng tube is dissipated.

Such a loss of kinetic energy is disadvantageous. for example, if the water, more or less freed from steam, continues to crculate by being ledthrough downcomers hack to the evaporating tubes, because on account of the check to the circulation, the mass of water must be accelerated again.

In contrast to such arrangements, this part oi the present invention is characterizecl by the fact that, over a sucently long stretch of the flowpath of the mixture, transfer ducts are provide& leading to a pipe or containe' and connected, to the mixtnre tube, so that over this Stretch the gas or vapor can freely separate and pass into the connected plpe or container from the licucl, which. continues to flow in the mixture tube.

In consequence of this arrangement, no separator ccntainer is interposed in the flow-path of the mixture, and in addition the tube traversecl by the mxture cloes not pass through a container.

In contrast to the prccesses o' separation carriec out in steam-separating drums and in known. steam driers, the separation of stearn and water according to this pari; of. the present in vention is not brought about through stopping or interrnptlng the flow of water, preferably ,I

nalz tme ls enectecl by connectng a riser tube to r In this section, example, leoo pipe is connecte to the n'nwre t he into vllnch issue holes or oncnings prcwcled in the neper wall of the mixture tuhe. e

From a mxture fiowing through a curved accorcl rg to this part the present "wen on stean can he separate& on the inner side of the cnrve since the water, under the action of cen trl l force, moves in contact With the outer hall of the curvecl tube.

lt is already linomi to Wthdraw steam on the Inner of a curvecl tulerom a mixtre of &team and. flowing the'ethrough. With this object, a tuhnlar connection is introduce& into the curvel tulle from the cuter side of the bend, which provided. near the inner wall of the cirrvec tube on the side turned away from the clirectlon ol flow with e small. inlet opening for the steam.

!a substantiel separatlon of steam from the moving water cannot, however, he eflected in this maner.

In contrast thereto, according to this part oi' the present invention. as great as possible a separaticn of steam ls efected by connecting to the lnner side of the curved tubeja lead-off pipe, into which an elcngated clischarge opening, comprising perforatcns provided in the inner Wall of the bend over a sufflcic-ntly long Stretch, discharges.

?m'thot ohects and advantages of the invention will appear' more fully from the following description, particularly when taken in conjunction with the accompanyng drawings which form aroma-7 a group of circulation units connected in series to form a coil with a horizontal axis.

Figura 4 shows a modification having a plurality of circulating units fed from a reservoir. Figure 5 shows diagrarnmatically, in vertical section. a further example of the new water-tube boiler. t

Figure 6 is a diagram of a part of the same in plan View.

Figuresm 8 and 9 are diagrammatic vertical sections through three further forms of construc- 'other form of the invention.

Figura ll is a diagram of a part of the same in plan view.`

Figures 12 to 17 show different forms of construction of the' separating apparatus, partly in holes or slits 5 opening thereinto.

elevation and partly in section.

Figura 18 is a cross 'section on the line iB-IS of Figure 17.

in the circulation units shown in Figures 1 to 4, the heated riser or steam generating tube is indicated at i, and the unheated or only slightly heated downcomer at 2. In the upper part of the unit, the riser is connected to the.downcorner by a bend having a large radius of curvature and at the bottom by a bend with a smaller radius of curvature, sudden changes of directionbeing thus avoided throughout so 'that a circulation unit is provided with a closed circulating path free from obstruction. i

By means of a pipe 3, feed water is fed into the downcomer 2 in the same direction as theflow therein. the steam 'generated in the riser part being led oiT at the upper intermediate part of the unit where the riser connects ,with the downcomer.

With this object, a lead-off pipe 8 is connected to the intermediate tube l which is provided with In addition, a connecting pipe 'lis provided between the steam outlet duct B and the downcomer 2, so that water condensed or entrained can 'escape into the downcomer.

By virtue of the bend of large radius, the steamwater mixture in the riser I is transrerred without 'substantial resistance to flow into the more or less horizontal length 4. in which it can continue fiowing at a high velocity. In this length of tube i a comparatively long path is provided in which steam can separate by passing through the openings 5' into the steam lead-off pipe 8.

The length within which the separation of turbed by steam-generating processes working g under other conditions of circulating andheating, so that no defiection of the flow of water occurs through suction due to other steam-generating tubes. I I

In the :form of the invention shown in Figure 3, three circulation units. each comprising a riser and a downcomer, are connected into a. group closed in itself. The first riser l is connected to the next downcomer 2, this downcomer to the second riser, this again to the next downcomer, this downcomer to the third riser and this to the thirri downcomer, which is connected back to the first riser.

The unit is red through thepipe &into the downcomer i which delivers into the first riser I only. On the other hand, steam is withdrewn through a lead-od pipo t provided at the upper part oi each individual circula'tion unit forrned of a riser and a downcomer.

The circuiation in an individual unit is in ths form no longer completely independent of the circulation in the other units. but the advantage is Secured that the total circulaticn is divided into individual circulations and each circuiation unit contains only a small mass of water, though variable between wide limits. and that at no point of the boiler can a large mass of water accumute which by its inertia could check the circula- As a modified iiorm, however, each downconer of a group may he ieri. as will be described bepassing through a trickle preheater in, for example, is heated by the steam in the reservoir 8. The feed pine is indicated at i2, and the steam pipe leading to the place of consumption at !3.

This reservoir is then connected with the cir'- culating units by the water inlet tubes which deliver into the downcomers. The feed is delivered into this reservoir and from it each unit takes the feed water required. In consequence. the water content in the tubes even with irregular feed or load varias less rapidly.

The water content of the boiler is in this way increased without exercising a disturbing ini fiuence on the circulating system. such a reservoir, to which a water-level indicator can be fitted, is advantageously applied to larger boilers with several circulating systems connected in parailel. The water lever in the reservoir can moreover, be subjected to larger variations or leveL without endangering the cooling of the in-' dividual units.

It is, therefore, possible with a new boiler providedwith this arrangement to withdraw suddenly, in a. manner known in itself, larger quantities of steam, without the necessity of immediateiy adjusting the firing and feed. since even with smaller water content o! the circulating' units. the upper -heated parte of the steam-generating tubes arestill well cooled. on the other hand, the possihility exists of reading boilers with reservoirs only'frqrn time to time.

`Obviously it is not necessary that all the steam pipes of the circulation units should be led to the reservoir. Ailthat is necessary is that a balance of pressure should be established between the reservoir and the 'circulation units, and for this purpose a connection of any sort between the steam lead-oil' sections of the circulation unit and the upper part of the rese'voir is sufficient.

In Figures 5 and 6, the risers I of the circulation units lie close together and form the wall of the combustion chamber |5, the circulation units being connected in series as already described with reference to Figure 3, in the case of a circution group comprising three units.

The groups of units are connected in a set to form an annular coil closed upon itself, water being fed into each third downcomer, or one of each group, in the direction of the fiow of fiuid therein. The feed water is fed into a ring !6, from which feed pipes IT lead to the proper downcomers. The steam generated in the risers is separated at the upper .part of each circulation unit and led off through ducts IS to the collector ring ia. From this ring I& steam passcs through a pipe 20 to a superheater 2! which is arranged in a fiue 22 connected to the combustion chamber, while in the fiue 22 above the superheater 2i a feed-water heater 23 is provided, from which a pipe 24 leads to the feed-water ring IE.

By thus connecting the new circulation units in series in such a way that the water content of the riser of a circulation unit, after separation of the steam, always fiows into the downcomer of the next unit and the downcomer of the last unit is connected with the riser oi the first unit, the sets of unit groups form a coil with horizontal nxis which can be closed upon itself. In ths way. a, tube boiler is obtained which units the characteristics of the coil boiler with vertical rising axis and of the tube boiler with a number of comparatively short riser tubes at a considerable angle.

In Figure '7, the feed-water heater is indicated at 25 and is formed as a pre-evaporator. The tubes leading the steam-water mixture from the preheater 25 are indicated at 26, the steam being .separated in these tubes and led through steam pipes 21 to the risers i of the circulating units.

Beyond the points where the steam pipes branch off, the tubes 28. connected to the tubes 25, contain water free from steam which is led into the downcomers 29 of the circulation units in the direction of the flow therein.

The circulation units can, by way of example, be arranged in an annulus as in Figures 5 and 6 or they can be arranged in any other suitable fashion. y

The steam generated in each circulation unit is led off from its upper part to a steam collector 30.

In F'igure 8, the wall surrounding the combustion chamber is formed of steam generating tubes arranged in a helieal coil having the form of a six-threaded screw, the individual coils or tubes of the wall being indicated by the numerals 3l to 36. Each of the six coils, according to the invention, is connected by an unheated downcomer to a circulation unit, ior example, the coil 3! is connected with the downconer 21. The uppermost part of the coil passes without any sudden change of direction into the downcomer 31, which is so bent down at its lower end that it leads without sudden change of direction to the lower end of the coil 31 forming its inlet.

In this way each coil forms the riser OT a circulation unit, the steam generated in this riser being led off at the upper end of the unit from the zone ot transition between the riser part and the downcomer part. The steam lead-off pipe of the unit to which the riser 3l corresponds is indicated at 38.

To the steam lead-off pipes of the six circulation units, tubes are connected in which the superheating is en'ected. The superheater tube connected to the pipe 38 is indicated at 39. The superheater 40 formed of convolutions of these connecting tubes, lies, in the example illustrated,

in a fiue 4l connected to the combustion chambe'. v

The steam led off from the circulation units of the steam-generating system flows therciore direct to the superheater.

In this form of the new boiler, notwithstanding the fact that the steam-generating tubes lie close together so as to form a wall, the boiler as compared with the single threaded coil has the advantage that it comprises only comparatively short tubes at a eonsiderable anglc with only a small resistance to fiow. Also, in such a coil system, the water fiows in parallel through the short circulating paths.

Only the steam generated is led off and as much water is fed into the system as is withdrawn in the form of steam. The circulating system remains the same, with the exception that the steam-generating tubes are substantially longer than the downcomers.

In Figures 9 and 10, circulation units highly heated to different degrees are connected in series.

In Figure 9 coiled tubes serve as risers, these tubes being wound, as in Figure 8. in the form of a six-threaded helix. The most highly heatcd coils 44 form the wall of the combustion chamber third circulation units; and these again are con- I nected to the downcomers 49 which are led back to the risers 44 of the first circulation units.

For the sake of clearness in the drawings, the downcomers 41, 48 and 49 are shown only by single lines, although actually six risers and six downcomers would be provided. The device then consists of a set of six groups of units, each group comprising oneunit in each coil.

The steam generated in the individual circulation units is led off at the upper part of each unit Feed as indicated by the arrows 50, 5I, 52. water is introduced only into the most highlyheated circulation units, and preferably into the downcomers 49 which lead back to the risers 44, whereby the eflicient cooling explained in the introduction to this specification is Secured with respect to the most highly heated tubes. The point of introduction of feed water to the circulation units is indicated at 53.

The hot gases at the upper end of the combustion chamber 43 pass under a cover 54, and thence in a downward direction through a fiue 55 to the lower end of a flue 56 which at its upper end is connected with the uptake 51.

It will be seen that the risers 44 of the first set of circulation units, which form the wall of the combustion chamber, are heated to the greatest extent and that the risers of the second set of units, which form a wall separating the fiues 56 are heated to a less extent; and that.

finally, the outermost risers 45 of the third set ot circulation units are heated to a still less extent by the already largely cooled combustion gases.

In the form oi the invention shown in Figures 10 and 11,- three groups of risers heated to diiferent degrees are provided as before, these risers being connected with their corresponding downcomers to form circulation units. Therisers are arranged round a combustion chamber so that the hot gases, therein rising rrom below, flow ever series of tubes formed hy the risers.` The risers ti lying nearest to the axis of the combustion chamber; are the most highly heated; the risers 62, next in order being heated less highly; and the risers '63, lying iurthest from the axis,

i are heated to the least extent. The correspond- All the risers and downcomers are connected in series, in a manner that will he cbvicus ironi Figure 11, so as to form sets of unit groups which in effect comprise one continuous cell. is ied into the downcorners ti& which lead to the most highly-heated risers ti', so that these, as

above explained, contain the largest quantity oi water. From each circulation unit iormed ci a rise' `and' downcomer, stea'm is led off at the upper part and separated' from the stream of water. such a steam lead-off pipe is indicated in Flgure lil at ti, and thefeed pipe connected to adowncomer tt at tt. The circulation units ti and t l are arranged at a somewhat higher level than the units ta, BE and these again somew hat higher than the units ta, tt. The apex of the circulating path of the most highly-heated unit thus lies at a somewhat higher level than that of the succeeding less highiy-heated unit in which the steam-water mixture 'is raised to a somewhat less extent. in this way, consideration is taken of the fact that the circuiating force is strongest in the riser which is heated to the greatest extent.

With individual circulating units thua connected in series to form a group, an advantageous form of the invention is obtained, inasmuch as the circulation units are heated less and less strongly according to their successive positions in series. the feed water being introduced into the unit heated to the highest extent. The largest quantity of fluid flows through the mest' highly heated riser so that an especially efllcient'cooling of the tube heated to the greatest extent, and consequentiy mostexposed to damage, is Secured.

While one form of Separator suitable'Ior use with water-tube boiiers in accordance with the present invention has been described with reference to Figure 2, it will be understood that many other constructional forms embodying the sanie principle of' maintaining the velocitycf flow of the water are possible. v

Thus, in the form shown in Figura 12, the length of tube 89 in which the separation of the steam is completed from the moving mixtu'e, is

arranged horizontaliy.

In orderto faciliate the separation ci' the steam,

the cross-section of the tube G@ is enlarged as' compared with 'the cross-section ci' the tuhes lt and 12.

The mixture, for example; any heated llcuid Feed-water length a. in the tube 69 pass through openings 13 in the upper tube wall to a lead-'off pipe-IL The individual openings through which y the steam separated from the moving waterpasses from the mixture tube into the lead-off pipe could be replaced by any other suitable arrangement which would provide open space in the tube wall at points spaced along the length of the tube.

In certain circumstances, a lengthwise section of the tube may be provided with an enlarged cross-section, in such a way that the steam may reely separate from the stream of i water over a sumciently long Stretch to a space inside the tube section, from which it passes to the lead-off tube.

such a form of Construction is shown in Figura 13. 'The section of tube whose cross-section is greater than the cross-section of 'the inlet tube 'iii and of the water-receiving tube 'it is indicated at li. a

Along the length a, steam from the stream of miitture can freely separate to the space provided in the upper part of the tube section 'li and from this space can iiow into the lead-off pine lE.

v 'in Figure 14, the separation of the steam from the mixture is completed along the length a, of a section of tube 'H of gradually increasing crosssection connected to the inlet tube lt.

At the end of the length in which separation is eitected, the tube il forks into a tube lt and a tuhe W. The water, without any change in its direction of flow, passes into the tube it, and the separated volatile constituerits are led ofl through the pipe lt. w

in the form shown in Flgure 15, the separation of the steam from the mixture is likewise eiiected along the length a 'of a tube section ll' of increasing cross-section connecting to the inlet tube 16. The tube section ll" passes, at the end of the length in which separation is ei'fected, into the tion 'il' of the tube 'it are on the other hand led of! through the pipe lt' bra'nching off in a reverse direction from the section ll'.

While in the constructional forms of the example described, it is assumed that the voiatile constituents pass ireelyupwards from the moving inixture and the water continues to flow in the lower part of the tube, Flgure 16 shows another term of construction in which the separation of the volatile constituents of the mixture flowing'in a curved tube takes place on the inner side thereoi'.

The 'tube bent into a circular are, for example, one convolution of a coil evaporator, is indicated by the numeral 80.

Under the action of centrifugal force, the iiquid is compelled to move to the outer side of the tube while the steam collects along the inner wall, separation being eficted along the length a. At this point, a lead-off pipe Bi is connected to the tube 80 on its inner side, into which issue t holes 82 provided in the innerwali of the bent tube co.

Figures 17 and 18 show a constructional form in which steam is separated from the water flowing through a tube and passed into a connected container, two mixture tubes connected to a common container 83 being shown in the example iiiustrated.

As the regions of separation are similarly arranged, it will be suflicient to describe one of them. The riser tube 84 passes at it's upperend into e. straight length of tube 85, which is connected through a bend 86 to a downcomer 81.

The upper wall of the length of tube 85 enters a slot provided in the wall of the container 83, the connection being made water-tight by a welded seam 88.

In the upper wall of the length of tube 85, holes or slits 89 are provided which open into the container 83.

The steam separated from the fiowing mixture along the length a can pass freely through the slits 85 into the container 83, While the water outside the container continues its course through the tube 85 and the bend 85 to the downcomer 81.'

While I have described herein certain forms of my invention, I wish it to be understood that I do not intend to limit myself thereby except within the scope of the appended claims.

I claim:

l. A water-tube steam generator, which in addition to the quantity of water continuously fed in and evaporated during one passage through the boiler, contains an additional mass of water, units comprising steam-generating tubes and downcomer tubes, means connecting said steameenerating tubes and said downcomer tubes the steam-generating tubes of each circulating unit being continuously connected with the downcomers of the next unit, to form a group of units having a substantially closed circulating path, and means in said connecting means to separate the steam from the water-steam nixture produced in said steam-generating tubes, whereby the water in said mixture after separation of steam thereirom may continue to flow through said downcomer tubes.

2. In a steam generator as claimed in claim 1, means to introduce feed water into a piurality of said units,

3. A water tube steam generator, which, in addition to the quantity of water continuously i ed in and evaporated during one passage through the boiler, contains a small additional quantity of water, comprising steam-generating tubes, and downcomer tubes, means connecting said steamgenerating tubes and said downcomer tubes to iorm circulating units, means in said connecting means to separate the steam from the Waterstcam mixture produced in said steam-generating tubes, whereby the water in said mixture after the separation of steam therefrom may continue to flow through said downcomer tubes, means to collect the steam separated by said separating means, and means independent of said collecting means to introduce feed water into the lower portion of at least some of said' circulating units.

4. A water tube steam generator, which, in addition to the quantity of water continuously fed in and evaporated during one passage through the boiler, contains a small additional quantity of water, comprising steam-generating tubes, and downcomer tubes, means connecting said steam-generating tubes and said downcomer 'tubes to form circulating units, in which the circulating water content of the steam generator is divided into a plurality of circulating units, means in said connecting means to separate the steam from the water-steam mixture produced in said steam-generating tubes, whereby the water in said mixture afterthe separation of steam therefrom maycontinue `to flow through said downcomer tubes, upper and lower headers, means connecting the steam separating means oi a plurality of said circulating units to said` upper header, means connecting said lower header to a plurality of said units, and means to feed water to said lower header.

5. A water tube steam generator, which, in addition to the quantity of water continuously ed in and evaporated during one passage through the boiler, contains a small additional quantity of water, comprising steam-generating tubes, and

downcomer tubes, means connecting said steamgenerating tubes and said downcomer tubes to form circulating units, in which the circulating water content of the steam generator is divided into a plurality of circulating units, means in said connecting means to separate the steam irom the water-steam mixture produced in said steam-generating tubes, whereby the water in said mixture after the separation of steam therefrom may continue to flow through said downcomer tubes, said units being disposed around an axis, upper and lower annular headers, means connecting the steam separating means of a plurality of said circulating units to said upper header, means connecting said lower header to a plurality of said units, and means to feed water to said lower header.

6. A water tube steam generator comprising a circulatory system of steam generating tubes, downcomer tubes, connecting means for said generator tubes and downcomer tubes. feed water tubes for said downcomer tubes, steam and water sepa'ating means in said connecting means, and means to conduct separated water to said downcomer tubes, said feedtubes being connected to the lower portions only of said downcomer tubes whereby low water columns are maintained in said downcomer tubes and the velocity of' separated water past said separating means is substantially retained in said circulatory system.

7. A water tube-steam generator comprising a furnace, steam generating tubes in said iurnace, downcomer tubes outside of said furnace, tubes connecting said generator tubes and said downcomer tubes, separating means in said connecting tubes to separate water from a steam-water mixture, steam collecting means connected to said separating means, means to conduct the separated water into said downcomer tubes, and means to introduce feed water into said downcomer tubes. A

8. A water tube steam generator as in claim 7, wherein the feed water tubes are separate from said steam collecting means and are connected to the' lower portions of said downcomer tubes.

9. A water tube steam generator, which, in addition to the quantity of water continuously fed in and evaporated during one passage through the boiler, contains a small additional quantity of water, comprising steam-generating tubes wound in the form of a multi-threaded coil, and downcomer tubes, means connecting said steamgenerator tubes and said downcomer tubes, means in said connecting means to separate the steam from the water-steam mixture produced in said steam-generator tubes, whereby the water in said mixture after the separation of steam therefrom may continue to flow through said downcomer tubes, means to conduct off the steam separated by said separating means, and means unconnected with said conducting means to introduce water into at least some of said tubes.

MARTIN som/mar. 

